Traffic signal housing and road sign obtained using high-strength fibre composite

ABSTRACT

Provided are a traffic signal housing and a road sign which are higher in weather resistance and lighter in weight as compared with conventional traffic signal housings and road signs using metal plates. A traffic signal housing and a road sign each made of a high-strength fiber composite in which a surface of a prepreg in which a thermoplastic resin has been combined with a sheet-shaped high-strength fiber including carbon fiber or basalt fiber has been coated with a thermosetting resin, wherein the prepreg is one prepared b thermally pressing a laminate in Which a sheet-shaped thermoplastic resin and said sheet-shaped high-strength fiber have been laminated together in a sandwich structure, are high in weather resistance to salt damage and so on, and moreover since they are lightweight, poles with reduced strength can be used therefor.

TECHNICAL FIELD (Priority Information)

This application claims the priority based on the Japanese patent application No. 2012-106148 filed on May 7, 2012. The contents of the Japanese application are incorporated herein by reference. This Japanese patent application has been registered on Feb. 1, 2013 as Japanese Patent No. 5188636.

The present invention relates to a traffic signal housing and a road sign.

BACKGROUND ART

Although light bulbs have heretofore been used as light sources of traffic signals located on roads, railroads, and the like, they have in recent years been being replaced by LEDs, which are lower power consuming and brighter. In exchanging a traffic signal, parts other than a light source are assembled again and reused.

Present traffic signal housings are usually constructed of metal plates such as iron plates and aluminum plates (see, for example, Patent Document 1) When metal plates are used for a traffic signal housing, the weight of a signal with ordinary three-color light emission parts is as large as about 10 to about 17 kg. Moreover, if arrow signs are added, the weight of the whole traffic signal increases. Therefore, the strength of a pole to support a traffic signal is required to be enhanced.

When metal plates are used for a traffic signal housing, the metal plates rust at coastal locations due to salt damage. Accordingly, routine rust inhibitor paint coatings are required, resulting in a problem of imposing high maintenance cost. Moreover, corroded metal plates are landfilled as industrial wastes because they are difficult to be recycled and cannot be burned.

PRIOR ART DOCUMENT Patent Document

Patent Document Japanese Utility Model Laid-open Publication No. H04-4396

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

It is an object of the present invention to provide as traffic signal housing and a road sign made of a high-strength fiber composite that is lightweight and excellent in weather resistance and durability to wind and rain, salt damage, and so on.

Solutions to the Problems

It was considered b the present inventors that a high-strength fiber composite capable of solving the above-described problems could be provided by using both a thermoplastic resin and a thermosetting resin simultaneously for high-strength fiber such as carbon fiber. Upon repeated intense study, the inventors found surprisingly that properties of resulting prepregs can vary significantly depending upon the method of combining a thermoplastic resin to a sheet-shaped high-strength fiber. Thus the present invention has been completed.

The present invention involves the following inventions.

<1> A traffic signal housing made of a high-strength fiber composite which comprising a surface of as prepreg in which a thermoplastic resin has been combined with a sheet-shaped high-strength fiber comprising carbon fiber or basalt fiber has been coated with a thermosetting resin, wherein the prepreg is one prepared by thermally pressing a laminate in which a sheet-shaped thermoplastic resin and said sheet-shaped high-strength fiber have been laminated together in a sandwich structure.

<2> The traffic signal housing according to <1>, wherein the thermoplastic resin is one selected from among acrylic resin, vinyl chloride resin, vinylidene chloride resin, polyacrylonitrile resin, polyamide resin, polypropylene resin, thermoplastic polyimide resin, polyethylene terephthalate resin and polycarbonate resin.

<3> The traffic signal housing according to <1> or <2>, wherein the thermosetting resin is one selected from among epoxy resin, phenol resin, thermosetting polyimide resin, unsaturated polyester resin, urea resin and melamine resin.

<4> The traffic signal housing according to any one of <1> to <3>, wherein the number of the laminations of the high-strength fiber sheet is 5 to 100.

<5> A road sign made of a high-strength fiber composite which comprising a surface of a prepreg in which a thermoplastic resin has been combined with a sheet-shaped high-strength fiber comprising carbon fiber or basalt fiber has been coated with a thermosetting resin, wherein the prepreg is one prepared by thermally pressing a laminate in which a sheet-shaped thermoplastic resin and said sheet-shaped high-strength fiber have been laminated together in a sandwich structure.

<6> The road sign according to <5>, wherein the thermoplastic resin is one selected from among acrylic resin, vinyl chloride resin, vinylidene chloride resin, polyacrylonitrile resin, polyamide resin, polypropylene resin, thermoplastic polyimide resin, polyethylene terephthalate resin and polycarbonate resin.

<7> The road sign according to <5> or <6>, wherein the thermosetting resin is one selected from among epoxy resin, phenol resin, thermosetting polyimide resin, unsaturated polyester resin, urea resin and melamine resin.

<8> The road sign according to an one of <5> to <7>, wherein the number of the laminations of the high-strength fiber sheet is 5 to 100.

Effects of the Invention

According to the present invention, there are provided a traffic signal housing and a road sign each made of a high-strength fiber composite that is lighter in weight and superior in weather resistance in the outdoors such as resistance to salt damage, and also in durability as compared with conventional traffic signal housings and road signs each using a metal plate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating one embodiment of a traffic signal using the traffic signal housing of the present invention.

FIG. 2 is a diagram illustrating one embodiment of the road sign of the present invention.

FIG. 3 is a diagram illustrating a step of producing a prepreg according to the present invention.

FIG. 4 is a diagram illustrating a state after coating a prepreg with a thermosetting resin.

EMBODIMENTS OF THE INVENTION (Traffic Signal Housing)

The traffic signal housing of the present invention is characterized by being made of a high-strength fiber composite which comprising a surface of a prepreg in which a thermoplastic resin has been combined with a sheet-shaped high-strength fiber comprising carbon fiber or basalt fiber has been coated with a thermosetting resin, wherein the prepreg is one prepared by thermally pressing a laminate in which a sheet-shaped thermoplastic resin and said sheet-shaped high-strength fiber have been laminated together in a sandwich structure (the fiber composite is hereinafter sometimes recited simply as “high-strength fiber composite”).

As will be discussed in more detail below, the high-strength fiber composite, which is the constituent of the traffic signal housing of the present invention, is high in mechanical strength and also high in weather resistance. Therefore, the fiber composite is suitable as a traffic signal housing material that needs to have strength high enough for withstanding a strong wind or a snowfall. Moreover, since the fiber composite is lighter in weight than metal plates which are materials of conventional traffic signal housings, it can reduce the required strength of a pole that supports a traffic signal, as compared with the case of using a metal plate.

The traffic signal housing of the present invention can be produced by combining high-strength fiber composites having been shaped into an appropriate shape by the shaping method described in detail below.

The traffic signal housing of the present invention can be used as a housing of a traffic signal in which a light bulb or an LED is used as a light emission part. Especially, a traffic signal using an LED light emission part is simple in the shape of its housing because the LED light emission part can have a plate shape and therefore the traffic signal housing of the present invention can suitably be used therefor. As to traffic signals using an LED, the housing for a traffic signal is usually painted in black so that drivers can easily verify that an LED light emission pan is on. When carbon fiber is used as the high-strength fiber in the traffic signal housing of the preset invention, there is an advantage that no further black painting is required because carbon fiber is black in color.

(Road Sign)

The road sign of the present invention is characterized by being made of a high-strength fiber composite which comprising a surface of a prepreg in which a thermoplastic resin has been combined with a sheet-shaped high-strength fiber comprising carbon fiber or basalt fiber has been coated with a thermosetting resin, wherein the prepreg is one prepared by thermally pressing a laminate in which a sheet-shaped thermoplastic resin and said sheet-shaped high-strength fiber have been laminated together in a sandwich structure. In FIG. 2 is illustrated one embodiment of the road sign of the present invention.

The road sign of the present invention is high in mechanical strength and also high in weather resistance because it is constituted of a high-strength fiber composite the same as that in the above-described traffic signal housing. Therefore, the road sign of the present invention has strength high enough for withstanding a strong wind and a snowfall. Moreover, since the fiber composite is lighter than a metal plate, the material of conventional road signs, it can reduce pole strength than use of a metal plate.

Since a road sign is in a plate-like shape, a plate-shaped high-strength fiber composite can be used without being subjected to shaping. Since the road sign of the present invention can use a plate-shaped high-strength fiber composite, it is easy to apply fluorine resin coating to the surface or to laminate a vinyl chloride-based film.

The traffic signal housing and the road sign of the present invention can be disposed by incineration or separated by a supercritical method and can he used as cement reinforcement after the separation (or the disposal by incineration) because of use of a high-strength fiber composite composed of carbon fiber or basalt fiber as their material.

(High-Strength Fiber Composite)

The high-strength fiber composite, which is the constituent of the traffic signal housing or the road sign of the present invention, is described in detail below. A “sheet-shaped high-strength fiber” is hereinafter sometimes recited as a “high-strength fiber sheet.”

The high-strength fiber composite according to the present invention is produced by coating, with a thermosetting resin, a surface of a prepreg prepared by combining a sheet-shaped high-strength fiber and a thermoplastic resin together. In other words, the high-strength fiber composite is in a hybrid laminated structure in which the inside is the prepreg, in which a sheet-shaped high-strength fiber and a thermoplastic resin have been combined together, with a thermosetting resin film formed on a surface of the prepreg.

The prepreg is a shaping intermediate base material in which a matrix resin has been combined with high-strength fiber.

Examples of a method for producing a prepreg in the case of using a thermoplastic resin as the matrix resin include (a) a method in which a high-strength fiber sheet is impregnated with a molten thermoplastic resin, (b) a method in which a thermoplastic resin is applied directly to a high-strength fiber sheet, (c) a method in which a laminate in which a sheet-shaped thermoplastic resin and a high-strength fiber sheet have been laminated in a sandwich structure is thermally pressed, and (d) a method in which high-strength fiber yarns and thermoplastic resin yams are twisted together to form textiles, which are then laminated and thermally pressed.

Among these, in a high-strength fiber composite is preferably used a prepreg prepared by (c) thermally pressing a laminate in which a sheet-shaped thermoplastic resin and a high-strength fiber sheet have been laminated in a sandwich structure. The sandwich structure referred to herein means a structure in which sheet-shaped thermoplastic resins and high-strength fiber sheets are laminated by turns.

Although the detailed reason is not clear, when a thermoplastic resin prepreg prepared by thermally pressing a laminate layered in a sandwich structure is used, the strength of a final product high-strength fiber composite tends to increase more stably its compared with thermoplastic resin prepregs prepared by other processes.

Conventionally, a high-strength fiber composite in which a carbon fiber sheet and a resin have been combined is widely used for such applications as housings of airplanes and so on due to their light weight and high durability. Options of the resin to be combined with a carbon fiber sheet include a thermosetting resin and a thermoplastic resin, which each have drawbacks. Specifically, while a thermosetting resin prepreg in which a carbon fiber sheet has been fixed with a thermosetting resin is cured by heating and reacting an unreacted thermosetting resin, the prepreg cannot be recycled if it is shaped into a desired shape and formed once by applying heat. Therefore, if a traffic signal housing or a road sign is produced using a thermosetting resin prepreg, it cannot be reused when a waste is generated upon exchanging. On the other hand, a thermoplastic resin prepreg can be transformed by applying heat of about 150° C. and various shapes can easily be made therefrom. In addition, since it is inferior in strength or weather resistance as compared with a thermosetting resin prepreg, there are no examples of practical applications to traffic signal housings or road signs.

In contrast, since the high-strength fiber composite according to the present invention is prepared by coating a surface of a prepreg in which a thermoplastic resin has been combined with a sheet-shaped high-strength fiber comprising carbon fiber or basalt fiber with a thermos cuing resin, wherein the prepreg is in a special structure produced by thermally pressing a laminate in which a sheet-shaped thermoplastic resin and said sheet-shaped high-strength fiber have been laminated together in a sandwich structure, it can be transformed into various shapes and it can be applied to a practical use level for traffic signal housings and road signs because of their high mechanical strength and weather resistance.

The configuration of the high-strength fiber composite according to the present invention is described in more details below.

(High-Strength Fiber Sheet)

As the high-strength fiber in the high-strength fiber sheet, carbon fiber, basalt fiber, glass fiber, polyimide fiber, aramid fiber, polyarylate fiber, and polyphenylene sulfide (PPS) fiber, for example, can be used. Among these, carbon fiber or basalt fiber is preferred because a high-strength fiber composite having particularly high rigidity and mechanical strength can be obtained therewith.

Carbon fiber is particularly preferably used because it is well balanced with respect to weight and strength and exhibits high affinity with any resin to be combined.

Today, traffic signal housings are painted in black in order to enable drivers to accurately verify illumination of an LED. When carbon fiber, which is black in color, is used as high-strength fiber, there is an advantage that a traffic signal housing can be used as received and is not required to be painted.

A carbon fiber yarn is indicated by 1 k, 3 k, 6 k, 12 k, or 24 k according to the number of carbon fiber filaments aggregating to form one yarn; for example, a 12 k carbon fiber yarn is a yarn made of 12000 filaments aggregated. Depending upon the number of laminations of the sheet-shaped carbon fiber in a prepreg, the carbon fiber yarn constituting the carbon fiber is preferably 6 k or more, and it is more preferable to use a carbon fiber yarn of 12 k or more.

Basalt fiber, which is an inorganic mineral fiber, is excellent especially in acid resistance and alkali resistance as well as in mechanical strength such as tensile strength and therefore is suitable for use under severe environment such as salt damage and acid rain. In addition, basalt fiber exhibits the same coefficient of thermal expansion as that of concrete and therefore is particularly suitable for reuse as a cement reinforcement after disposal.

When a high-strength fiber composite is used for outdoor applications such as a traffic signal housing and a road sign, it is required to have strength high enough for withstanding a strong wind and a snowfall.

In order to enhance mechanical strength of a high-strength fiber composite, high-strength fiber sheets that constitute a prepreg are laminated. If, however, the number of laminations is excessively large, the high-strength fiber composite becomes excessively large in thickness and therefore becomes difficult to shape. Accordingly, the number of laminations of the high-strength fiber sheet that constitutes the prepreg is preferably within the range of 5 to 100. Lamination of less than five sheets may result in insufficient strength. Since the pressing, pressure becomes higher as the thickness increases, it becomes difficult to shape if the number of laminations exceeds 100.

The thickness of one high-strength fiber sheet is usually about 2 to about 20 mm.

(Thermoplastic Resin)

The thermoplastic resin is determined according to affinity with the high-strength fiber to be combined as a prepreg. Examples of preferable thermoplastic resin include acrylic resin, vinyl chloride resin, vinylidene chloride resin, polyacrylonitrile resin, polyamide resin, polypropylene resin, thermoplastic polyimide resin, polyethylene terephthalate resin and polycarbonate resin. Among these, acrylic resin is one of the suitable resins because of good affinity with carbon fiber and basalt fiber.

The thickness of the thermoplastic resin sheet, which can vary depending upon, for example, the thickness of the high-strength fiber sheet to be combined as a prepreg, is usually about 100 μm to about 10 mm.

(Production of Prepreg)

A prepreg can he produced, for example, with an apparatus having the configuration illustrated in FIG. 3. A prepreg in a desired shape can be obtained by heating a laminate comprising a sheet-shaped thermoplastic resin and a high-strength fiber sheet laminated in a sandwich structure in a pre-heating section is heater section) and then shaping it at a pressing section into a prescribed shape.

For example, when the high-strength fiber composite is used as a traffic signal housing, a thermoplastic resin prepreg can be shaped into a shape appropriate as a traffic signal housing member with a press, followed by coating it with a thermosetting resin described later. Methods for pre-heating a laminated prepreg include a method involving heating a mold and a method not involving heating a mold and any one can be used; when an acute angle is made with a press mold, a method not involving heating is preferred because a product can be released easily from the press mold and is hardly deformed.

When the high-strength fiber composite is used as a road sign, the prepreg can be shaped into a plate form.

(Physical Properties of Prepreg)

The tensile strength of a prepreg is determined mainly by the tensile strength of a high-strength fiber sheet. The strength, which can vary depending upon the type, the fiber density, the thickness, and so on of the high-strength fiber sheet, is usually about 500 to about 2000 kg/mm².

As the strength, there is frequently used a theoretical value calculated from the number of yarns whose strength per yarn is disclosed in a catalog of the high-strength fiber used for the high-strength fiber sheet published by the yarn manufacturer. When a textile is produced, crossings of weft and warp yarns form elevations and depressions to lower the strength. Therefore, the value obtained by multiplying a value 90% of the theoretical value by 70% is frequently taken as an actually measured value.

(Thermosetting Resin)

The high-strength fiber composite is formed by coating a surface of the above-described prepreg with a thermosetting resin. A schematic diagram is shown in FIG. 4. Possession of a coating film of a thermosetting resin on a surface remarkably improves the surface hardness and the chemical durability of the high-strength fiber composite as compared with a prepreg haying no coating films.

The thermosetting resin is not particularly restricted as long as it is a resin that can undergo a crosslinking reaction by the aid of heat to form a three-dimensional crosslinked structure. Examples of such a thermosetting resin include epoxy resin, phenol resin, thermosetting polyimide resin, unsaturated polyester resin, urea resin, and melamine resin, and their modified forms are also available. Moreover, two or more resins may be used in mixtures. Such thermosetting resins may be either one that is cured well by heating or one that is cured well at about room temperature with blend of a curing agent, a cure accelerator, etc.

Epoxy resin and thermosetting polyimide resin, which are strong to an ultraviolet ray, high in weather resistance excellent in dynamic properties, and excellent in balance of adhesion with carbon fiber, are particularly preferably used.

The method for applying a thermosetting resin to a surface of a prepreg is not particularly restricted, and a publicly known method such as a roll coating method, a spin coating method, a wire bar method, a dip coating method, an extrusion method, a curtain coating method, a spray coating method, a flow casting method, a bar coating method, a gravure coating method, a doctor blade method, or a die coater method can suitably be adopted. Especially, spray coating is preferred because a thermosetting resin can thereby be applied uniformly to a surface even if the object to be coated has a structure with elevations and depressions.

The thickness of the thermosetting resin to be formed on the prepreg surface, which can vary depending upon the application, is usually about 100 μm to about 10 mm. For example, however, when the traffic signal housing or the road sign of the present invention is used in seashore where there is salt damage or in an area with strong wind, the thermosetting resin may be thicker.

Cure of the thermosetting resin may be performed at normal temperature, but it is preferable to cure the resin by placing it in a sealed oven and then heating in order to achieve uniformization. As to the heating temperature, a temperature suitable for the thermosetting resin used may appropriately be chosen.

INDUSTRIAL APPLICABILITY

The traffic signal housing and the road sign of the present invention are excellent in mechanical strength and weather resistance, and because of the use of a lightweight high-strength fiber composite as a base material, they have high weather resistance to salt damage or the like. Moreover, they are lightweight and therefore poles with more reduced strength can be used as compared with conventional traffic signal housings and road signs in which metal plates are used. Accordingly, the traffic signal housing and the road sign of the present invention are expected to be spread widely. 

1. A traffic signal housing made of a high-strength fiber composite which comprising a surface of a prepreg in which a thermoplastic resin has been combined with a sheet-shaped high-strength fiber comprising carbon fiber or basalt fiber has been coated with a thermosetting resin, wherein the prepreg is prepared by thermally pressing a laminate in which a sheet-shaped thermoplastic resin and said sheet-shaped high-strength fiber have been laminated together in a sandwich structure.
 2. The traffic signal housing according to claim 1, wherein the thermoplastic resin is one selected from among acrylic resin, vinyl chloride resin, vinylidene chloride resin, polyacrylonitrile resin, polyamide resin, polypropylene resin, thermoplastic polyimide resin, polyethylene terephthalate resin and polycarbonate resin.
 3. The traffic signal housing according to claim 1, wherein the thermosetting resin is one selected from among epoxy resin, phenol resin, thermosetting polyimide resin, unsaturated polyester resin, urea resin and melamine resin.
 4. The traffic signal housing according to claim 1, wherein the number of the laminations of the high-strength fiber sheet is 5 to
 100. 5. A road sign made of a high-strength fiber composite which comprising a surface of a prepreg which as thermoplastic resin has been combined with a sheet-shaped high-strength fiber comprising carbon fiber or basalt fiber has been coated with a thermosetting resin, wherein the prepreg is one prepared by thermally pressing a laminate in which a sheet-shaped thermoplastic resin and said sheet-shaped high-strength fiber have been laminated together in a sandwich structure.
 6. The road sign according to claim 5, wherein the thermoplastic resin is one selected from among acrylic resin, vinyl chloride resin, vinylidene chloride resin, polyacrylonitrile resin, polyamide resin, polypropylene resin, thermoplastic polyimide resin, polyethylene terephthalate resin and polycarbonate resin.
 7. The road sign according to claim 5, wherein the thermosetting resin is one selected from among epoxy resin, phenol resin, thermosetting polyimide resin, unsaturated polyester resin, urea resin and melamine resin.
 8. The road sign according to claim 5, wherein the number of the laminations of the high-strength fiber sheet is 5 to
 100. 